There is a solitary T1 hypointense, T2 hyperintense lesion in the white matter of the left temporal lobe. The lesion demonstrates a central nodule of ring enhancement with no elevation of CBV or diffusion restriction. The lesion partially suppresses on FLAIR imaging and exerts minimal positive mass effect with no subfalcine, tonsillar or uncal herniation. A prominent peripheral rim of high FLAIR signal persists. MR spectroscopy demonstrates reversal of the choline to creatine ratio with elevated NAA within the left temporal lobe lesion. The remainder of the brain is unremarkable.
Conclusion: FLAIR rim sign is characteristic of a DNET although the degree of enhancement is not typical. Possibilities also include other low-grade tumours (e.g. ganglioglioma or pleomorphic xanthoastrocytoma). A higher grade tumour is also a possibility.